A two-stage vibration isolation device for absolute gravity measurement

Abstract

The present invention relates to a two-stage vibration isolation device for absolute gravity measurement, comprising a base; an elastic suspension mechanism, mounted on the upper end of the base; a fixed suspension plate, vertically fixed on the upper end of the base; a first-stage pendulum, comprising a vertical moving frame and a suspension frame, the upper and lower ends of the moving frame are correspondingly and movably connected to the upper and lower ends of the fixed suspension plate through an upper connecting rod and a lower connecting rod movably connected thereto, and together form a parallelogram frame structure, the suspension frame is elastically connected to the elastic suspension mechanism, a feedback magnetic cylinder is mounted on the lower end, and a feedback coil is arranged on the base; a second-stage pendulum frame is mounted on the moving frame for vertical rotation, and is connected to the suspension frame through an elastic member; a displacement detection system is connected to the feedback coil; and a corner cone prism is mounted on the second-stage pendulum frame. Advantages: It can limit the degrees of freedom in other directions except the swinging direction, eliminate the amount of rotation in the swinging process, and solve the problem of angle deflection in the vibration isolation system using a horizontal pendulum structure.

Description

Technical Field

[0001] The invention relates to the technical field of mechanical measurement, and in particular to a two-stage vibration isolation device for absolute gravity measurement. Background Art

[0002] Traditional absolute gravimeters use free fall plus optical interference to measure gravitational acceleration g. The test optical path includes a test prism and a reference prism. During the measurement process, the test prism performs free fall motion and is not affected by ground vibration; however, the reference prism will be affected by ground vibration, causing changes in the test optical path and interfering with the measurement. Therefore, corresponding stabilization measures must be taken for the reference prism to suppress vibration interference.

[0003] Only the FG series absolute gravimeters produced by Micro-G in the United States have been successfully commercialized in the world. This series of absolute gravimeters is considered to be the most technologically mature absolute gravimeters in the world. However, the vibration isolation system of this series of gravimeters has a complex structure, a large size, and is technically blocked from the outside world. Many domestic research institutions have studied two-stage vibration isolation devices based on vertical pendulum structures, but the rotation generated by the vertical pendulum structure during movement will affect the vibration isolation effect.

[0004] To this end, it is necessary to design a device with a simple structure, easy operation, and the ability to eliminate the rotation during the swinging process and solve the problem of angular deflection in the vibration isolation system using the horizontal pendulum structure, so as to provide technical support for the development of high-precision absolute gravimeters. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a two-stage vibration isolation device for absolute gravity measurement, which effectively overcomes the defects of the prior art.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] A two-stage vibration isolation device for absolute gravity measurement comprises a base; an elastic suspension mechanism, the elastic suspension mechanism is mounted on the upper end of the base; a fixed suspension plate, the fixed suspension plate is vertically fixed to the upper end of the base; a first-stage pendulum, the first-stage pendulum comprises a vertical moving frame and a suspension frame, the moving frame is arranged between the fixed suspension plate and the elastic suspension mechanism, and the upper and lower ends of the moving frame are respectively movably connected to the upper and lower ends of the fixed suspension plate through an upper connecting rod and a lower connecting rod movably connected thereto, and the fixed suspension plate, the moving frame, the upper connecting rod and the lower connecting rod together constitute a parallelogram frame structure, and the suspension frame is fixed The second-stage pendulum frame is fixed on one side of the mobile frame close to the elastic suspension mechanism and is elastically connected to the elastic suspension mechanism. A feedback magnetic cylinder is installed at the lower end of the suspension frame, and a feedback coil corresponding to the feedback magnetic cylinder is provided on the base; a secondary pendulum frame, the secondary pendulum frame can be installed on the mobile frame so as to rotate up and down, and is connected to the suspension frame through an elastic member; a displacement detection system, the displacement detection system is connected to the feedback coil and is used to monitor the relative displacement difference between the secondary pendulum frame and the mobile frame, and feed it back to the feedback coil; a corner cube prism, the corner cube prism is installed on the secondary pendulum frame.

[0008] Based on the above technical solution, the present invention can also be improved as follows.

[0009] Furthermore, the elastic suspension mechanism includes a support frame, an adjusting rod and a spring. The support frame is fixed to the upper end of the base. The adjusting rod is vertically assembled on the upper end of the support frame and its height is adjustable. The spring is vertically arranged and its upper and lower ends are connected between the lower end of the adjusting rod and the upper end of the suspension frame.

[0010] Furthermore, both ends of the upper connecting rod and the lower connecting rod are rotatably connected to the upper and lower ends of the movable frame and the fixed suspension plate through flexible bearings respectively.

[0011] Furthermore, the secondary pendulum frame is movably connected to a side of the movable frame close to the fixed suspension plate.

[0012] Furthermore, the elastic member is a leaf spring, and two ends of the leaf spring are respectively connected to the upper ends of the suspension frame and the secondary pendulum frame.

[0013] Furthermore, the above-mentioned displacement detection system is a capacitive displacement detection system, which includes a detection circuit connected to the above-mentioned feedback coil, and a capacitor fixed plate and a capacitor moving plate respectively connected to the above-mentioned detection circuit. The above-mentioned movable frame is equipped with a capacitor installation frame distributed in parallel with the above-mentioned secondary pendulum body frame, the above-mentioned capacitor fixed plate is installed on the upper part of the above-mentioned capacitor installation frame, and the above-mentioned capacitor moving plate is installed on the above-mentioned secondary pendulum body frame at a position close to the above-mentioned capacitor fixed plate.

[0014] The beneficial effects of the present invention are: simple structural design, convenient assembly, strong reliability, and the ability to well limit the degrees of freedom in directions other than the swinging direction, eliminating the amount of rotation during the swinging process, and solving the problem of angular deflection in the vibration isolation system using a horizontal pendulum structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic structural diagram of a two-stage vibration isolation device for absolute gravity measurement of the present invention;

[0016] Figure 2 It is a structural schematic diagram of a first-stage pendulum in a two-stage vibration isolation device for absolute gravity measurement of the present invention;

[0017] Figure 3 It is a schematic structural diagram of a secondary pendulum in a two-stage vibration isolation device for absolute gravity measurement of the present invention;

[0018] Figure 4 It is a schematic structural diagram of the flexible bearing in the two-stage vibration isolation device for absolute gravity measurement of the present invention.

[0019] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0020] 1. Base, 2. Elastic suspension mechanism, 3. Fixed suspension plate, 4. Primary pendulum, 5. Feedback magnetic cylinder, 6. Feedback coil, 7. Secondary pendulum frame, 8. Elastic member, 9. Corner cone prism, 21. Support frame, 22. Adjustment rod, 23. Spring, 41. Moving frame, 42. Suspension frame, 43. Upper connecting rod, 44. Lower connecting rod, 10. Displacement detection system, 102. Capacitor moving plate, 103. Capacitor mounting frame. DETAILED DESCRIPTION

[0021] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0022] Example: Figures 1 to 3As shown, the two-stage vibration isolation device for absolute gravity measurement of this embodiment includes a base 1; an elastic suspension mechanism 2, the elastic suspension mechanism 2 is installed on the upper end of the base 1; a fixed suspension plate 3, the fixed suspension plate 3 is vertically fixed on the upper end of the base 1 and is located on one side of the elastic suspension mechanism 2; a first-stage pendulum 4, the first-stage pendulum 4 includes a vertical moving frame 41 and a suspension frame 42, the moving frame 41 is arranged between the fixed suspension plate 3 and the elastic suspension mechanism 2, and its upper and lower ends are movably connected to the upper and lower ends of the fixed suspension plate 3 respectively through an upper connecting rod 43 and a lower connecting rod 44 movably connected thereto, and the fixed suspension plate 3, the moving frame 41, the upper connecting rod 43 and the lower connecting rod 44 together form a parallelogram frame structure. The suspension frame 42 is fixed to one side of the mobile frame 41 close to the elastic suspension mechanism 2 and is elastically connected to the elastic suspension mechanism 2. A feedback magnetic cylinder 5 is installed at the lower end of the suspension frame 42, and a feedback coil 6 corresponding to the feedback magnetic cylinder 5 is provided on the base 1; a secondary pendulum frame 7, the secondary pendulum frame 7 is installed on the mobile frame 41 so as to be rotatable up and down, and is connected to the suspension frame 42 through an elastic member 8; a displacement detection system 10, the displacement detection system 10 is connected to the feedback coil 6, and is used for monitoring the relative displacement difference between the secondary pendulum frame 7 and the mobile frame 41, and feeding back to the feedback coil 6; a corner cube prism 9, the corner cube prism 9 is installed on the secondary pendulum frame 7.

[0023] The working steps and mechanism of the whole device are as follows:

[0024] 1) If Figure 1 As shown, after assembling the various structural components of the device, when the ground vibrates, the bottom plate 1 and the fixed suspension plate 3 will vibrate accordingly, and under the action of the parallelogram formed by the primary pendulum 4 and the fixed suspension plate 3, the primary pendulum 4 and the secondary pendulum frame 7 only move in the vertical direction without rotating;

[0025] 2) The displacement detection system is used to measure the displacement difference between the primary pendulum 4 and the secondary pendulum 9, and the displacement difference is transmitted to the feedback coil 2. The feedback coil 2 and the feedback magnetic cylinder 61 act to generate a feedback force acting on the primary pendulum 6, so that the primary pendulum and the secondary pendulum form an equivalent long-period elastic system, thereby effectively isolating the ground vibration and keeping the corner cube prism 93 installed on the secondary pendulum 9 in an absolutely stationary state.

[0026] The whole device has a simple structural design, is easy to assemble, and has high reliability. It can effectively limit the degrees of freedom in directions other than the swinging direction, eliminate the amount of rotation during the swinging process, and solve the problem of angular deflection in the vibration isolation system using a horizontal pendulum structure.

[0027] As a preferred embodiment, the elastic suspension mechanism 2 includes a support frame 21, an adjusting rod 22 and a spring 23. The support frame 21 is fixed to the upper end of the base 1. The adjusting rod 22 is vertically assembled on the upper end of the support frame 21, and its height is adjustable. The spring 23 is vertically arranged, and its upper and lower ends are connected between the lower end of the adjusting rod 22 and the upper end of the suspension frame 42.

[0028] In this embodiment, the elastic suspension mechanism 2 has a simple structure and is easy to assemble. A hanging point that is easy for spring assembly is provided at the upper end of the suspension frame 42.

[0029] More specifically, the support frame 21 is an inverted U-shaped frame structure, and its upper end has a horizontal horizontal and vertical section. The horizontal and vertical section is provided with a through hole that passes through the upper and lower parts. The adjusting rod 22 passes through the through hole. The position corresponding to the through hole on either side of the horizontal and vertical section is threadedly connected with a bolt that extends into the through hole. The bolt is adjusted so that it is abutted against the adjusting rod 22, thereby maintaining the height of the adjusting rod 22 after the height is adjusted.

[0030] As a preferred embodiment, both ends of the upper connecting rod 43 and the lower connecting rod 44 are rotatably connected to the upper and lower ends of the movable frame 41 and the fixed suspension plate 3 through flexible bearings, respectively.

[0031] More specifically, the sides of the mobile frame 41, the upper connecting rod 43, and the lower connecting rod 44 are all provided with round holes with notches, and through holes and threaded holes are respectively provided on both sides of the notches. The fixed suspension plate 3 is a "mouth"-shaped metal frame, and round holes with notches are provided on the sides of both sections. Round holes with notches are provided on the sides of both ends of the secondary pendulum frame 7; wherein, Figure 4 As shown, the flexible bearings 11-1, 11-2, 11-3, 11-4, and 11-5 include a bearing sleeve 111, a bearing sleeve 112, and a vertically distributed thin constant elastic metal sheet 113. The bearing sleeve 111 and the bearing sleeve 112 can rotate around the intersection of the vertically distributed thin constant elastic metal sheet 113 at a certain angle.

[0032] It should be noted that the fixed suspension plate 3, the movable frame 41, the upper connecting rod 43 and the lower connecting rod 44 are connected by flexible bearings to form a quadrilateral frame structure. When in a stationary state, it is a rectangular structure. When external vibration occurs, under the action of the flexible bearing, the rectangle becomes a parallelogram, and the upper connecting rod 43 and the lower connecting rod 44 will deviate from the horizontal position, but the vertical movable frame 41 is always parallel to the fixed suspension plate 3 and remains vertical, because the fixed suspension plate 3 is fixed and in the vertical direction during installation, which ensures that the first-stage pendulum 4 as a whole only moves in the vertical direction without rotating. Therefore, the displacement measured by the capacitor is only the relative displacement between the first-stage pendulum 4 and the second-stage pendulum 9, and does not include the displacement caused by rotation, which reduces the influence of cross-coupling between other degrees of freedom.

[0033] As a preferred embodiment, the secondary pendulum frame 7 is movably connected to a side of the movable frame 41 close to the fixed suspension plate 3 .

[0034] In this embodiment, the secondary pendulum frame 7 is reasonably distributed, which facilitates the operation experiment of the device.

[0035] As a preferred embodiment, the elastic member 8 is a leaf spring, and both ends of the leaf spring are respectively connected to the upper ends of the suspension frame 42 and the secondary pendulum frame 7 .

[0036] In this embodiment, the use of the leaf spring is compatible with the entire device, and the assembly is simple and convenient.

[0037] More specifically, a leaf spring mounting shaft is provided at the upper end of the fixed suspension plate 3, and a leaf spring end mounting block is provided at the upper end of the secondary pendulum frame 7. The leaf spring is placed above the suspension frame 42 and the secondary pendulum frame 7, and both ends are respectively connected to the leaf spring mounting shaft and the leaf spring end mounting block.

[0038] As a preferred embodiment, the displacement detection system 10 is a capacitive displacement detection system, which includes a detection circuit connected to the feedback coil 6, and a capacitor fixed plate and a capacitor moving plate 102 respectively connected to the detection circuit. The movable frame 41 is provided with a capacitor mounting frame 103 which is distributed in parallel with the secondary pendulum frame 7. The capacitor fixed plate is mounted on the upper part of the capacitor mounting frame 103, and the capacitor moving plate 102 is mounted on the secondary pendulum frame 7 at a position close to the capacitor fixed plate.

[0039] In this embodiment, the capacitive displacement detection system is a prior art, wherein the detection circuit is a circuit of a conventional capacitive displacement detection system, and the displacement difference is obtained by detecting the relative displacement between the electric fixed plate and the capacitive moving plate 102, and the information is fed back to the feedback coil 6. The feedback coil 6 adjusts its feedback action parameter according to the signal, thereby adjusting the force acting on the entire primary pendulum 4 through the feedback magnetic cylinder 5, so that the primary pendulum 4 and the secondary pendulum frame 7 constitute an equivalent long-period elastic system, thereby effectively isolating the ground vibration and keeping the corner cone prism 9 installed on the secondary pendulum frame 7 in an absolutely stationary state.

[0040] More specifically, the fixed suspension plate 3, the secondary pendulum frame 7 and the capacitor installation frame are all horizontally arranged strip frame structures.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A two-stage vibration isolation device for absolute gravity measurement, characterized in that: include: Base (1); An elastic suspension mechanism (2), the elastic suspension mechanism (2) being mounted on the upper end of the base (1); A fixed suspension plate (3), wherein the fixed suspension plate (3) is vertically fixed to the upper end of the base (1); A first-stage pendulum body (4), the first-stage pendulum body (4) comprising a vertical movable frame (41) and a suspension frame (42), the movable frame (41) being arranged between the fixed suspension plate (3) and the elastic suspension mechanism (2), the upper and lower ends of the movable frame (41) being movably connected to the upper and lower ends of the fixed suspension plate (3) respectively through an upper connecting rod (43) and a lower connecting rod (44) movably connected thereto, and the fixed suspension plate (3), the movable frame (41), the upper connecting rod (43) and the lower connecting rod (44) together constitute a parallelogram frame structure, the suspension frame (42) being fixed to a side of the movable frame (41) close to the elastic suspension mechanism (2) and being elastically connected to the elastic suspension mechanism (2), a feedback magnetic cylinder (5) being installed at the lower end of the suspension frame (42), and a feedback coil (6) corresponding to the feedback magnetic cylinder (5) being provided on the base (1); A secondary pendulum frame (7), the secondary pendulum frame (7) is mounted on the movable frame (41) so as to be rotatable up and down, and is connected to the suspension frame (42) via an elastic member (8); A displacement detection system (10), the displacement detection system (10) being connected to the feedback coil (6) and used for monitoring the vertical relative displacement difference between the secondary pendulum frame (7) and the moving frame (41), and feeding back the difference to the feedback coil (6); A corner cube prism (9), wherein the corner cube prism (9) is mounted on the secondary pendulum frame (7).

2. A two-stage vibration isolation device for absolute gravity measurement according to claim 1, characterized in that: The elastic suspension mechanism (2) comprises a support frame (21), an adjustment rod (22) and a spring (23); the support frame (21) is fixed to the upper end of the base (1); the adjustment rod (22) is vertically mounted on the upper end of the support frame (21) and its height is adjustable; the spring (23) is vertically arranged, and its upper and lower ends are connected between the lower end of the adjustment rod (22) and the upper end of the suspension frame (42).

3. The two-stage vibration isolation device for absolute gravity measurement according to claim 1, characterized in that: The two ends of the upper connecting rod (43) and the lower connecting rod (44) are rotatably connected to the upper and lower ends of the movable frame (41) and the fixed suspension plate (3) respectively through flexible bearings.

4. The two-stage vibration isolation device for absolute gravity measurement according to claim 1, characterized in that: The secondary pendulum frame (7) is movably connected to a side of the movable frame (41) close to the fixed suspension plate (3).

5. A two-stage vibration isolation device for absolute gravity measurement according to claim 4, characterized in that: The elastic member (8) is a leaf spring, and the two ends of the leaf spring are respectively connected to the upper end of the suspension frame (42) and the secondary pendulum frame (7).

6. A two-stage vibration isolation device for absolute gravity measurement according to any one of claims 1 to 5, characterized in that: The displacement detection system (10) is a capacitive displacement detection system, comprising a detection circuit connected to the feedback coil (6), and a capacitor fixed plate and a capacitor moving plate (102) respectively connected to the detection circuit, a capacitor installation frame (103) arranged in parallel with the secondary pendulum frame (7) being installed on the mobile frame (41), the capacitor fixed plate being installed on the upper part of the capacitor installation frame (103), and the capacitor moving plate (102) being installed on the secondary pendulum frame (7) at a position close to the capacitor fixed plate.

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